In testing IC devices, an automatic test handler is frequently used in combination with an IC tester to automatically provides IC devices (DUT) to be tested to a test position at the test head of the IC tester. There are generally two types of test handlers, a vertical transfer type handler wherein the IC devices to be tested are transferred in a vertical direction with their own gravities and a horizontal transfer type handler wherein IC devices placed on a tray or carrier module are transferred in a horizontal direction to the test position. The test handler of this invention is directed to horizontal transfer type handler.
In a typical horizontal transfer type test handler, IC devices to be tested are aligned on a tray in a loading area and picked, one by one, and transferred to a test head of an IC tester and placed on a test socket of the test head by a pick and place mechanism or a robot hand of the test handler. The tested IC devices are taken out from the test head and transferred to an unloading area and placed on a tray based on the test results.
In this type of handler, the overall paths wherein the IC devices are transferred and handled are lengthy and complicated. Thus, it requires a relatively long time for positioning the IC device to the test socket and start testing and for returning the tested IC device to the unloading are. In the semiconductor test industry, the overall time required for handling the IC device other than the time required for an actual device testing is called an index time.
Since the index time is not the actual time for the device testing, it is considered that the shorter the index time, the higher the test efficiency of the test handler. However, as noted above, the conventional test handler requires a relatively long index time because of the length of device transfer paths and complicated movements of the test handler.
Further, a modern IC device has a large number of pins with a small pitch. In addition, each pin is very small in size and is not mechanically strong. Thus, the test handler for testing such devices having a large number of pins, an ability of precise positioning is required to accurately placing the IC device on a test position, typically a test socket having a large number of corresponding contact pins. However, because the fine positioning of the IC devices needs complicated adjustments of various components, errors tend to arise in placing or extracting the IC devices with respect to the test socket, which deform the pins of the IC devices and make the test unavailable.
An example of a conventional horizontal type test handler is shown in FIG. 5. FIG. 5 is a schematic diagram showing a plan view of a test handler 100. A tray 20 having the IC devices to be tested is transferred from the loading area to a transfer station 21 (dotted line) where each of the IC devices is picked by a suction end 10 of a pick and place mechanism and transferred to a test socket 31 positioned at the test head of an IC tester.
The suction end 10 is provided on a contact arm 50 to be movable along the arm 50 in a back and forth direction (Y). The contact arm 50 can move in a right and left direction (X) along rails 40. Thus, the suction end 10 can freely take a position by the movement in the X and Y directions on a surface of the test handler 100.
By placing the IC device on the test socket 31, an IC tester (not shown) supplies test signals to the IC device on the test socket 31 and the resulted output signals from the IC device are evaluated by the IC tester by comparing them with expected data. The suction end 10 picks the IC devices that have been tested and transferred to a tray on a receiving station 22 (dotted line) and place the IC devices depending on the test results. The IC devices on the tray are transferred to an unloading area 23 where the IC devices are unloaded with the trays for the next process, such as a packing and shipping for customers.
FIG. 4 is a side view showing an example of a suction end used in the pick and place mechanism of FIG. 5. In this example, the suction end 10 is provided with an air pipe (not shown) connected to an air cylinder to provide a suction air force. When the suction air force is at work, the suction end 10 attracts the IC device below and picks up the IC device by the suction air force. As noted above, the suction end 10 is movable in the X and Y directions on the test handler. Thus, the suction end 10 transfers the IC device one by one from the transfer area 21 to the test socket 31 and from the test socket 31 to the receiving station 22 by the X-Y movements as noted above.
During this process involved in the conventional test handler, the operation of placing the IC device on the test socket 31 sometimes fail because of an inaccurate positioning of the IC device with respect to the test socket. Such inaccurate positioning occurs basically because the suction end 10 picks the IC device while moving in the X and Y directions in relatively high speed and thus suction end 10 may not accurately contact the ideal position of the IC device when placing the IC device. Further, the suction end 10 may fail to contact the accurate position of the IC device because of the poor surface condition of an IC device or other factors such as mechanical vibrations.
Therefore, in the conventional test handler as exemplified in FIGS. 4 and 5, a relatively large index time is needed for supplying IC devices to be tested to the IC socket as a result the test efficiency is limited by the index time. In addition, positioning error sometimes occur because of the inaccuracy of picking the IC devices by the pick and place mechanism of the test handler.